Air seeders for seeding agricultural crops commonly include furrow openers mounted on a wheel supported implement frame for injecting agricultural products into the soil, and a cart with a number of separate containers or compartments for carrying the different agricultural products such as fertilizers, seeds, chemicals, and the like that are to be applied to the soil. A distribution network is operative to convey agricultural products from the various containers to the desired furrow opener locations.
The cart can be towed behind the implement frame or in front of the frame between the towing tractor and the frame. Where the cart is behind the frame, often a trailer carrying liquid fertilizer is towed behind the cart.
The different agricultural products are applied to a field at rates that can vary from a few pounds per acre to a few hundred pounds per acre, and so the containers are typically provided in different sizes. A typical air seeder cart will have three to five containers, with capacities ranging from several hundred cubic feet down to 50 or 60 cubic feet. Typically the containers are provided by a large tank divided into compartments, with fill hatches at the top of each compartment, and hoppered floors sloping down to a metering device at the bottom of each compartment.
When seeding canola for example, urea nitrogen fertilizer may be applied at 200 pounds per acre, sulphur fertilizer at 100 pounds per acre, phosphate fertilizer at 50 pounds per acre, and canola seed at four pounds per acre. Thus to seed 100 acres requires 20,000 pounds of urea fertilizer, 10,000 pounds of sulfur fertilizer, 5000 pounds of phosphate fertilizer, and only 400 pounds of canola seed. The different products then are placed into the different containers on the air seeder cart such that the highest use product goes into the largest container, the next highest use into the second largest, container, and so forth.
These fertilizers are generally transported in bulk form, and are moved into the hatches at the top of the compartments by a conveyor. Because of the relatively low quantity required and the relatively high value, canola seed is most commonly transported in bags which are carried to the seeder on a truck bed and manually opened and emptied into the seed compartment of the air seeder cart. These bags of canola and like agricultural products typically weigh about 50 pounds.
For this reason, and because canola is a common crop and prevalent in certain farming areas, some air seeder manufacturers provide a small container at the rear of the air seeder cart with a relatively low fill opening so that a truck can be backed up to the small container and the bags conveniently emptied into the container without climbing to an elevated hatch. The rear location is aligned with the conduits carrying the air stream and so allows the canola to be metered downward out of the container and into the air stream conduit extending under the container.
Seeding operations for other crops may also conveniently include an agricultural product with a low application rate that could conveniently be carried in the small low compartment. A problem with present low slung air seeder cart containers is that access to the location at the rear of the cart is hampered when the air seeder cart is towed between the tractor and the implement frame, and also in a tow behind cart where it is desired to tow a liquid fertilizer trailer, or some like equipment, behind the cart.
Application rates can be monitored to ensure accuracy. U.S. Pat. Nos. 7,523,710 and 7,765,944 to Wilson disclose a weighing system for a grain drill type seeding implement that displays the weight of seeds in the seed hopper. The method of the Wilson invention comprises setting the application rate control at an estimated position to apply a desired rate of seed, driving the drill along the field to seed an area, checking the acreage counter to determine the area seeded, determining from the initial and final displays the weight of seed applied to area seeded, and dividing to determine the weight of seed applied to the seeded area, and thus determining the weight of seed applied per acre, which is the application rate. The actual application rate is compared to the desired rate, the rate control is adjusted accordingly, and the process is repeated until the operator is satisfied that the actual rate is satisfactorily close to the desired rate.
The Wilson system is shown on a grain drill where the amount of seed carried in the seed hopper is quite small, but such weighing systems have been adapted to the large present day air seeders described above. Generally speaking, the accuracy of the weighing system decreases as the weight of the container being weighed increases. When weighing a grain drill seed hopper full of seed with a total weight of 2,000 pounds, a ten pound difference in weight is 0.5% of the total, while weighing an air seeder product container full of seed with a total weight of 20,000 pounds, a ten pound difference in weight is 0.05% of the total. The problem of accurately determining weight is accentuated if it is desired to determine weight while the air seeder is moving along the field and bouncing forces are typically encountered.
The required accuracy also varies depending on the application rate. Where for example it is considered satisfactory if the actual rate is within 5% of the desired rate, and the application rate is 300 pounds per acre, a difference of 15 pounds per acre could be acceptable, but where the application rate is 3.0 pounds per acre, a difference of 0.15 pounds per acre would be required.